The present invention relates to a film forming method for coating a photo-resist film or an anti-reflective coating on a layer (such as a semiconductor layer, an insulating layer, an electrode layer, or the like) formed on a surface of a substrate or a substrate for a liquid crystal display (LCD).
A photo-lithography technique is used in a process for manufacturing a LCD, like in a process for manufacturing a semiconductor device. In the photolithography technique for a LCD, a resist film is formed on a glass substrate and is subjected to pattern exposure and further to development. The semiconductor layer, the insulating layer, the electrode layer, or the like is selectively etched to form thin films and electrode patterns made of ITO.
In general, a so-called spin-coating method is used in case of applying a resist solution onto a LCD substrate. As shown in FIG. 1A, a substrate G is suctioned and maintained by a spin-chuck 701 in the spin-coating method, and both of a solvent and a resist solution 9 are dropped onto a rotation center portion of the substrate G. Subsequently, as shown in FIG. 1B, an upper opening is closed with a lid 713, and a rotation cup 711 and a spin chuck 701 are synchronously rotated. In this manner, as shown in FIG. 2A, the resist solution 9 is diffused from the rotation center portion to the peripheral portion and is thereby coated over the entire upper surface of the substrate G.
When the resist solution 9 must be diffused so as to draw a circle covering the four corner portions of the substrate as shown in FIG. 2B if the resist solution 9 should be applied to the entire substrate G, since the substrate G has a rectangular shape. In the case of diffusing the resist solution to the hatched regions R1 to R4 in the figure, the resist solution 9 is wasted.
However, if the supply amount of the resist solution 9 is decreased too much, the resist solution 9 does not sufficiently reach the corner portions of the substrate G. Therefore, it is conventionally necessary to supply an excessive amount of resist solution 9, and about 90% of the supply amount of the resist solution 9 is disposed of.
In case where the resist is coated in spin-coating method, however, the resist film is thickened to rise at the peripheral edge portion of the substrate due to influences from the surface tension after rotation stops to stop the centrifugal force or as the time is elapsed although the film thickness is uniform immediately after the film is coated. Also, in this method, an excessive portion of resist is shaken off by rotation of the substrate, and the portion of resist thus shaken off is diffused onto the back surface of the substrate so that the resist may stick to unnecessary portions.
Thus, a non-uniform thick film formed at the peripheral portion of the substrate and a resist sticking to the back surface thereof cause generation of particles in a later step of conveying the substrate, and may further soil devices for conveying the substrate.
Therefore, after a resist is coated on the surface of the substrate, processing of removing unnecessary resists sticking to the peripheral edge portion and the back surface of the substrate. This processing is performed after coating the resist, in a manner in which the substrate is conveyed to a resist remover unit adjacent to the resist coating unit, a resist remover nozzle comprising a solvent supply portion and a solvent suction portion is moved along the peripheral edge of the substrate, a solvent for the resist is supplied, and simultaneously, the resist dissolved by supply of the solvent is suctioned and removed.
However, in case of removing a resist using the apparatus as described above, the resist coating unit requires an additional equipment so that the size of the equipment must be inevitably enlarged. In addition, the nozzle must be moved with the substrate inserted in a narrow gap between the solvent supply portion and the solvent suction portion of the resist remover nozzle. Therefore, the accuracy of the positions of the substrate and the nozzle relative to each other must be high. Demands for such position accuracy become higher and higher as the size of the substrate has come to be enlarged in recent days.